unable to import vcards into address book including birthdays

I recently upgraded to Lion. (in meantime I did a complete fresh Lion installation twice)

The same problem occurs:

Before I installed Lion I exported all my address book data into vcard-Format.

Each vcard can be opened for example with "textedit" and everything is fine.

But when I try to import these vcards in the new Lion address book all data is imported

except the birthdays. I am still able to refresh the birthday data manually.

Moreover after installing Lion Server the birthday field is switched off. I am no even more able

to type in the birthday data manually.

Anyone an idea?